When your zoning reform to allow a new kind of housing works, you don't need fancy statistics to prove that it works. Exhibit C: ADU applications & completions in California are up many times the pre-reform rate. https://twitter.com/dagarciajr/status/1301207804129099776

Exhibit B: Palisades Park allows side-by-side duplexes by right in most of the city. The city is FULL of these, with the result that population has nearly doubled since it was first 'built out'. https://www.google.com/maps/@40.845167,-73.9901678,3a,75y,110.08h,94.05t/data=!3m6!1e1!3m4!1spQGSRlSWxOYbFaLyWpYvUg!2e0!7i16384!8i8192

Exhibit A: In 1998, Houston cut it's minimum lot size to 3,500 sq ft or less, with tiny setbacks and a 75 foot height limit (or no limit). The result is thousands of new townhouses on subdivided single-family lots in desirable neighborhoods.

By contrast, Minneapolis' dearth of triplex applications, unless that changes in the next year, indicates that something about its reform hasn't worked. You don't need me to run a fancy study on this. http://www.citypages.com/news/triplex-building-permits-requested-in-minneapolis-this-year-3/572278171